The rapidly growing privately held company has kept a relatively low public profile even as it has emerged as the nation’s largest seller of electronic health records software to physicians offices, outpacing larger and better known rivals such as Epic Systems and GE Healthcare. But the Westborough company’s name recognition may soon increase now that it’s poised to enter the consumer health arena.

The company is expected to disclose Wednesday that it is investing $25 million to develop and market “patient engagement tools” through a health and online wellness business based at a new building set to open next month across the street from eClinicalWorks’s corporate headquarters. The tools will include an app for iPhones and other mobile devices, giving patients access to their medical records, letting them keep track of medicines and test results, and enabling them to ­e-mail doctors with questions.

The company’s move is part of a broader trend toward greater transparency in health care, a field that has shown stubborn resistance to the kind of plain English communications and easy-to-access information consumers have come to expect in most businesses. Spurred by the federal health care overhaul and the push to control costs, state governments are setting up online exchanges to help residents buy insurance, health insurers are rolling out programs to help members find doctors, and doctors themselves have begun giving patients more information.

“I’m a strong believer that technology is a catalyst for change,” said eClinicalWorks cofounder and chief executive Girish Kumar Navani, who has been the driving force behind its expansion into the consumer business. “Technology is the underpinning of change.”

While there already are hundreds of health care apps — many of them free — most are designed to provide information about medical conditions and help people monitor diets or fitness programs. But there are seldom doctors behind such apps.

By contrast, the eClinicalWorks app will be “interoperable” with the records of its customers — about 72,800 physicians offices serving some 8 million consumers nationwide — who are betting improved communications between doctors and patients will ultimately make for better health outcomes.

Six months ago, eClinicalWorks launched a website, jointhenetwork.com, to allow doctors to share data online with the specialists to whom they refer patients.

Doctors will pay eClinicalWorks to make their patient records available online and on mobile devices, a service that will be offered without charge to patients. The reason: Doctors know they will increasingly be measured by healthy outcomes as insurance reimbursements shift from the traditional fee-for-service ­model to so-called global contracts. Under such arrangements, insurance companies give providers fixed budgets to take care of patients and ­reward them for saving money and minimizing hospital stays.

“The approach of eClinicalWorks is to differentiate itself with the ease with which providers can add these tools to their existing functionality,” said Judy Hanover, research director for technology research firm IDC Health ­Insights in Framingham. “This is an attempt to make relationships with patients more sticky in the new health care environment.”

Software companies like eClinicalWorks and athenahealth Inc. of Watertown have been disruptive forces in the electronic medical records market.

While established rivals gained footholds sooner with large health care organizations — selling computer hardware, practice management software, and services — the upstarts have been able to undercut them on pricing by offering programs stored on the Internet rather than in-house computer servers. Their software also handled a broader range of functions — scheduling and claims submissions as well as billing and coding — and was sold aggressively to small and midsized practices in addition to larger ones.

“I love the competition,” ­Navani said. “I love to win every single competition. But I am very patient.”

Industry giants GE Healthcare and Allscripts Healthcare Solutions still lead the pack in overall revenues from the sale of electronic health records hardware, software, and services to physicians practices, according to IDC estimates for 2011, the most recent year for which data is available (eClinicalWorks ranked fifth). But the larger companies derive much of their revenue from legacy hardware systems that customers are gradually replacing.

In the fast-growing software-only segment, estimated at $914 million last year, eClinicalWorks topped the IDC list. “The company has managed to succeed by making substantial improvements to its functionality that allow it to serve large, complex practices while remaining competitive with pricing virtually identical to that offered in 2007,” Hanover wrote in a December report on eClinicalWorks, which rang up sales of more than $210 million in 2011.

The company, which is creating a campus in Westborough, also has sales and software development offices in New York, California, Georgia, and Illinois. It has hired 80 people for its new health and online wellness business and expects to add 20 more jobs by the end of March. Overall, eClinicalWorks has about 2,150 employees, including 85o in Westborough.

Josh Archambault, director of health care policy for the ­Pioneer Institute in Boston, a public policy research group, said transparency tools offered by health care providers are “a good move from a customer service perspective, but I don’t think they will necessarily lead to a decrease in health care costs” unless providers share more information about prices and do more to promote preventive care.

Navani acknowledged the eClinicalWorks mobile app won’t initially include cost and quality information, but said they will be the inevitable byproduct of such technology.

“Providers are very protective now about not wanting to share [pricing] numbers,” he said. “That’s going to change, but it’s going to take a while. Within 12 months, we’re going to be talking about better pricing visibility. That’s because the consumers are demanding it.”